Means of reducing NVH in gears 2

[Mechie100]

I understand that the transfer gear can be a big source of noise in a automotive transmission. In a new test transmission, I have improved the gear manufacturing accuracy to the point that a 1 or 2 micron difference in gear geometry is the difference between the noisy and the quiet gears. Since this is not possible in a production environment, is there anything else I can do.

On a side note, will a austempered ductile iron gear improve noise transmission over the current cast iron gear design.

 

[MikeyP]

Some other possibilites...
1. Redesign the gear to improve the tooth contact ratio.
2. Reduce misalignment in the gear pair by stiffening the shafts or altering the bearing preloads
3. Reduce the gear pair's sensitivity to misalignment by adjusting the gear tooth profile (crowning/barrelling etc)

M

--
Dr Michael F Platten

 

[Wicsteve]

You might check the Ohio State University site "

http://gearlab.org/".

This site is for their gear noise constortium.

 

[muellerAlan]

I think you should know what is the main cause for the gear noise.
Sometimes, it is not just because of the gear manufacturing accuracy, but the mount precision which will cause unbalance.
My suggestion is to do vibration measurement and using cepstrum and envelop analysis method to locate the main vibrating place.

Regards

Alan Mueller

 

[Tmoose]

If there are resonances/ringing then the cast iron's slightly better damping might make it "better."
If the various panels of the gear case are resonating or ringing then damping them or re-tuning can get a 10 dB reduction or so.

 

[Rob45]

While it's certainly worthwhile to have gears as quiet as possible - within the limits of production gear-making capabilities - what you really want to do is reduce the apparent gear noise at the passenger's/operator's ears.
So in addition to paying careful attention to shaft and gear cluster rigidity, to avoid exciting noise-making torsional modes, you want to have a quiet gearcase, and to reduce the noise path transmissibility.
That is: use cast iron for the case, because of its greater damping, do analysis of the case to find where it needs to be ribbed to reduce ringing, and assure that, in addition to having compliant gearbox mounts, the control connection(s) to the box are sufficiently isolated not to provide a transmission path.
Good luck!

 

[Mechie100]

Thanks everyone for your comments.